Using multilevel modeling of state-level economic data and individual-level exit poll data from the 2000 Mexican presidential election, we find that income has a stronger effect in predicting the vote for the conservative party in poorer states than in richer states—a pattern that has also been found in recent U.S. elections. In addition (and unlike in the U.S.), richer states on average tend to support the conservative party at higher rates than poorer states. Our findings are consistent with the 2006 Mexican election, which showed a profound divide between rich and poor states. Income is an important predictor of the vote both at the individual and the state levels.
Here’s the paper, and here’s the key graph:
The little circles in the plots show the data from the exit poll from the 2000 election (average vote plotted vs. income category within each state, with size of the circles proportional to the number of survey respondents it represents). Party is coded as 1=PRD, 2=PRI, 3=PAN, so higher numbers are more conservative. The solid line in each plot represents the estimated relation between vote choice and income within the state (as fitted from a multilevel model). The gray lines represent uncertainty in the fitted regression lines.
The graph shows the 32 states (including Mexico, D.F.) in increasing order of per-capita GDP. The slopes are higher–that is, income is a stronger predictor of the vote–in poor states. Income is a less important predictor in the rich states (except for the capital, Mexico, D.F., which has its own pattern).
Here’s a plot of the slopes vs. per-capita GDP in the 32 states:
The conservative party did better with rich voters everwhere, but individual income is a much stronger predictor of the vote in poor states than in rich states. This is similar to the pattern we found in the U.S. One difference between the two countries is that in the U.S., the conservative party does better in the poor states, but in Mexico, the conservative party does better in the rich states. But at the level of individual voting, the patterns in the two countries seems similar.
We plan to replicate our study with 2006 exit polls, once we can get our hands on the data.
This is great. Congratulatons on your study. It's great to see determined, well informed and tooled people doing interesting political science!
I tried to send a trackback here from Fruits and Votes, but for some reason they never seem to work to Moveable Type blogs.
The most relevant thing I had to add (a question, really) at my post was:
"…the authors use a left-right scale that places the PRD at the left, PRI in what they call the “blurry center,” and PAN at the right. Nothing at all wrong with that ideological description, but is this the expected relationship of income level to the vote? I would think not: the poorest Mexicans probably have the strongest tendency to vote PRI, with the PRD strongest in the lower-middle classes (at least in 2006)."
Also of potential interest, the 2006 three-party dispersion graphs prepared by one of my regular commentators.
Interesting point. We did, in fact, do an analysis of PRI compared to all the other parties (in parallel to the plots in Figure 5 of the paper. PRI voting in 2000 was indeed negatively correlated with individual income. That is, the slopes were negative for the within-state logistic regressions predicting PRI vote from individual income. When comparing slopes across states (as in the Figure 5 plots), there was no consistent pattern with state income.
And, yes, trackback doesn't seem to work anymore, unfortunately.
"…the authors use a left-right scale that places the PRD at the left, PRI in what they call the “blurry center,” and PAN at the right".
I am not sure this is an apt description of the 2000 election. At least for the 2000 election, political competition in Mexico mostly took place on a pro-regime (pro-PRI)/anti-regime (anti-PRI) dimension – and not on a standard left/right economic redistribution dimension.